January 1, 2000: In the space of one second, the next millennium was cast into unfathomable scope

Inside a mountain somewhere in Texas a massive clock is clinking into existence. Housed in a cave deeper than the pyramids are tall, the sixty-metre high timepiece is a day's walk from anywhere. Behind a steel door, visitors will find a spiral staircase cut into rock by giant robotic chainsaws. They will climb to a winding platform to rotate a lever that lifts the four-thousand-five-hundred-kilogram weight drives that power the clock, along with thermal energy gathered from the mountaintop.

Bells will chime in three-and-a-half-million different sequences as decades, centuries and millennia pass by. This is not the largest clock in the world, but it is the longest. Created by a team of polymaths, inventors, engineers, machinists, stonecutters and a billionaire who is passionate about the future, this clock will keep time for ten-thousand years. It is a bulwark against the end of history.

The clock is the brain child of a US think-tank that, along with other determined futurists from around the globe, is trying to encourage constructive long-term thinking in a population increasingly averse to looking ahead.

Back in the olden days - 1964 - one of the great futurists, science-fiction writer and inventor Arthur C. Clarke described his vision of what was to come, at the World's Fair in New York. His predictions ranged from the bizarre (the creation of a slave race of bio-engineered super chimpanzees as home helps) to the prescient (a world perhaps fifty years hence in which we would be able to instantly contact each other from anywhere on Earth, "even if we don't know their actual physical location".) Nor was he alone in his imaginings. Inspired by the impending millennium, people conjured holidays under the sea, space tourism and food that could be printed. Preparations were made for pandemics and total network collapse.

But as the clocks ticked over to January 1, 2000, a certain change slipped by quietly. The cultural turning point that had once been sixty, thirty or ten years hence was suddenly a thousand years ahead. In the space of one second, the next millennium was cast into unfathomable scope - and the future began to shrink.

These days, it seems, our imaginations can barely keep up with the present. The pace of new developments is so quick that it's becoming difficult to imagine what the next five years will bring, let alone the next fifty or the next five hundred. Social media, multitasking, job insecurity and information overload all conspire to keep us revving frantically in the present. But to prepare for scenarios such as climate change, asteroid impacts and space travel, forward thinkers insist that we must keep imagining long-term scenarios.

Which is what I am doing now with Charlotte Hajer.

Hajer appears to me as a collection of pixels, arranged in such a way as to represent letters on a screen - very much like the letters you are reading now. Clarke was right. Hajer and I do not need to commute, we simply communicate. Hajer is in San Francisco writing from a desk at an organisation called the Long Now Foundation. (These are the people building the enormous clock.) Hajer's job is to drum up funding for this and other projects (one of these, the Rosetta Project, aims to assemble the largest digital library of the world's languages, living and dead), and to make sure that people like me are thinking and talking about them. Now more than ever.

From her distant terminal Hajer's letters blink across continents to Australia: "The year 2000 was such a big milestone that we stopped looking past it".

As a child Hajer was excited about the future. She was interested in astronomy, and in SETI's search for extraterrestrial life. She dreamed of being part of the first manned flight to Mars in the 2020s: "It seemed like such a long way off. There was something satisfyingly concrete yet mysterious about the fact that I could imagine being part of this future scenario".

But this kind of dreaming has shifted since the turn of the millennium, she says. And while those at Long Now consider the speed and churn of cities to be a largely positive force, Hajer acknowledges that many people are not convinced. Along with our accelerating world and shrinking attention spans, Hajer acknowledges "a creeping sense of pessimism that occludes our ability to imagine the future".

It is happening in Australia too.

Julia Cook is conducting a study of how young adults, aged eighteen to thirty-four, imagine the future. She is completing a PhD in the School of Social and Political Sciences at the University of Melbourne. Most of Cook's interviewees imagine an apocalyptic end-point within the next hundred to five hundred years. They predict humanity will survive beyond a crisis, but they cannot imagine the aftermath. Cook's research has shown that we conceive time-scales in a social, cultural context.

There is a popular belief that humanity is at the end of history. It is difficult to imagine the future when you think you are heading towards a destruction of your own making.

But even before the onset of the twenty-first century, a kind of popular short-term thinking had emerged in cities such as New York. In 1978, composer, artist and music producer Brian Eno dubbed the New York lifestyle the "short now". It was fast, exciting and temporary: no one seemed to think even two years ahead. In 1996, Eno joined founding members Stewart Brand and Danny Hillis to develop the beginnings of a very long-term cultural institution. Long Now was born.

Alexander Rose is the executive director of the Long Now Foundation and the manager of the Clock project; When he was a child he assumed the future would end in nuclear Armageddon. After the Cold War, United States television still ran advertisements on what to do in the event of a nuclear bomb. The Clock project resonated with Rose, he says, because it is fundamentally about hope. He is helping Danny Hillis, the Clock grand designer, to complete the engineering and build the structure.

The Long Now Foundation chose to focus on a time frame of ten-thousand years because, while expansive, it is still human in scale. Rose believes ten-thousand years is long enough to speak to the imagination, while being conceivable in a way that a hundred-thousand or a million is not: "If we chose millions or billions of years it is so dwarfing to the human experience it is hard to feel responsibility and consequence."

But imagine we must, say the futurists, because our imaginations are powerful.

Prophecies have a way of creating the conditions for their own fullment. In 1945, Sir Arthur C. Clarke cast his most famous vision of the future. He described the communication satellite in detail. Many considered it a farce, but twenty years later the first commercial communication satellite was launched

Similarly, Eno's dream of the Long Now Foundation took about twenty years and a team of people to manifest. He called the dream "an invisible force, which pulls us forward. By this process it starts to come true. The act of imagining something makes it real."

This, of course, suggests we need to be careful what we imagine.

Peter Ellyard is a futurist based in Melbourne. In his work he advises the United Nations on climate change and biodiversity and has run government planning departments for more than thirty years. There are not many things that interest everybody, he says, but the future is one of them.

"If you add up all the time you spend thinking about your future, you'll find it's at least fifty per cent of your total waking hours." We shape the future daily through small decisions such as which book to read next.

But the real issue is not how much we think about the future, but how we think about it. How far ahead do we think? What are our motivations? Are we driven by greed or are we altruistic? Do we, like many of our politicians, focus on short-term gain, or do we keep an eye to long-term benets? Most of us, says Ellyard, tend to focus on the next few days. But it is by creating a clear vision, he argues, that we can begin to shape the future. The questions we ask ourselves are important. Rather than simply wonder, "what will the future be like?" he says, we might ask, "what do I want the future to be like?"

And to further anchor these imaginings in concrete outcomes, he suggests that we consider the future in terms of grandchildren and great-grandchildren. Call it enlightened self-interest. In planning a future that includes future generations, we also benet those of us here now.

The see-saw of Long Now time tilts on an axis that places our present era at the centre of history. On one side of the seesaw we have the beginnings of civilisation, with the domestication of plants and animals. In the centre we have an accelerating world where everything is possible but in which the idea of the end of history has taken hold of the collective imagination. On the other side of the see-saw we have something undefined that stretches out over the next ten-thousand years. It could be interstellar travel in slinky silver outfits and colonised planets powered by cold fusion. It could be cities void of people, where office buildings have been transformed to grow food for residents in surrounding suburbs.

No one at Long Now is sure when the Clock will be completed. The project is not to be rushed. But those involved believe the idea alone is already creating the intended effect.

The point is that the ten-thousand Year Clock encourages people to feel that we have a future ahead of us, a future to think and fantasise about.

And now, from rough sketches to a cave in the Texas desert, the ten-thousand Year Clock is gradually becoming real. Its creators hope it will be the first of many such clocks. A second is already planned for a mountaintop in eastern Nevada.